In an analysis or examination in the biochemical field or the immunological field, liquid of a sample or a reagent is dispensed into sample containers through a suction discharge operation. For example, in this suction discharge operation, liquid of a sample or a reagent, diluted solution, or cleaning solution stored in many small holes of many test tubes or microplates is sucked into a suction discharge nozzle, and the sucked liquid is discharged into other containers or small holes. Automation of this suction discharge operation is accomplished by implementing a suction discharge system including a suction discharge nozzle movable in the depth direction (Z direction) of a container and in the plane direction (X-Y direction) where many containers are arranged laterally and longitudinally, and a pump connecting to the nozzle via a pipe.
The suction discharge system moves the suction discharge nozzle downward into a container, and puts the nozzle tip end into liquid in the container, so as to suck the liquid. In general, at the time of moving the nozzle downward, a slight clearance is secured between the nozzle tip end and the bottom surface of the container, so as to prevent damage to the nozzle tip end and the bottom of the container due to collision therebetween. A sufficient clearance between the nozzle tip end and the bottom surface of the container facilitates positioning of the nozzle tip end in the Z direction and reduces variation in the size of sample containers due to mass production, and also reduces strictness of positioning the sample containers in the suction discharge system.
Patent Literature 1 discloses a method for preventing damage to the nozzle, and when the nozzle tip end collides with an obstacle, this method moves the nozzle and the pipe upward so that the pipe abuts to a spring-loaded earth plate, thereby stopping the aim from moving downward. Patent Literature 2 discloses a method for allowing a nozzle tip end to elastically contact with a bottom surface of a container at slow speed so as to suck slight amount of liquid stored in the container without causing deformation, damage or fatigue fracture to the nozzle and/or containers. Patent Literature 3 discloses that, for the purpose of retaining a displacement state of a relative height between a needle guide and a needle, there are provided a needle, a guide provided to the needle whose relative height is variable at a predetermined amount, means for urging the guide downward and a needle guide holder. Patent Literature 4 discloses a method of moving a movable body apart from a nozzle receiver when a nozzle tip end abuts to an obstacle, so that the nozzle moves in the reverse direction to the movement of the nozzle receiver. Patent Literature 5 discloses a method of configuring a nozzle holder for holding a nozzle to be slidable so as to adjust the reference height of the nozzle tip end relative to the X-Y plane with high accuracy.